The occurrence of a strong earthquake often induces regional co-seismic deformation and stress changes,which also changes the stress state of fault zones and influences the seismic activity.At present,according to the existing fault slip model,researchers have been able to calculate co-seismic,post-seismic displacements and stress changes,and further apply the concepts of stress trigger to analyze the distribution of aftershocks and earthquake risks.Actually,there were many historical strong earthquakes,for example,the Haiyuan Ms8.5 earthquake in 1920,which is one of the biggest earthquakes all over the world.However,due to limitations in recordings of seismic data,only simple uniform fault slip models were proposed based on empirical formula or geological survey.In order to understand the influence of historical earthquakes on the following earthquakes more accurately,more accurate fault slip models are needed.Based on the previous research and general distribution of seismic slip and deep seismic reflection profile,we take Haiyuan Ms8.5 earthquake as an example and try to build the fault slip model.At the same time,simple and complex fault slip models with global co-seismic heterogeneous ellipsoid earth model with high precision topography are constructed,respectively.By calculating the co-seismic displacements and stress changes triggered by Haiyuan Ms8.5 earthquake,we found the complex fault slip model is much closer and more practical to the field surface dislocation.Moreover,we further calculate the stress changes and Coulomb failure stress changes of the major active faults in recent 100 years in the northeastern Tibetan Plateau due to the Haiyuan Ms8.5 earthquake.The preliminary results show that there are some significant differences in near field between simple and complex fault slip models,and no obvious difference in far fields.%大地震的发生会引起区域位移场和应力场发生变化,进而改变区域内及临近断层的应力状态和地震活动性.目前,研究学者可据已有的断层滑动模型来计算分析大地震同震应力变化,同时采用库仑应力触发理论来进一步分析震后余震分布和断层危险性.然而,历史上曾经发生过不少大地震,例如,1920年的海原Ms8.5大地震,是全球范围内少见的特大地震之一.局限于无确切的地震台站地震波等资料,前人在研究历史地震的影响时往往给出一些简单的断层滑动模型,将断层面上错动量视为均匀分布.为更准确地了解历史地震对后续地震的影响,基于前人研究和一般地震滑动形态分布规律及地震反射剖面等资料,以海原Ms8.5大地震为例,探讨了如何建立海原大地震断层滑动模型,并分别搭建了简单断层滑动模型和复杂断层滑动模型的全球同震横向不均匀并行椭球型地球模型.通过对海原Ms8.5地震的同震位移场和应力场的计算,发现采用复杂断层滑动模型比简单断层滑动模型地表位错分布更切合实际.同时,进一步计算和分析了此次大地震对青藏高原东北缘近100年历史地震和周围断层的应力触发作用,得出断层滑动模型对同震计算结果的影响集中在发震断层附近而对远场影响较小.
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